Mercury vapor lamp seasoning and sealing method



Dec. 13, 1966 H. D. FRASER ETAL MERCURY VAPOR LAMP SEASONING AND SEALING METHOD Filed Jan. 9, 1964 EXHAUST D ETECTOR BAKING a SEASONING NITROGEN FILL TIP-OFF OVEN UNLOAD EXHAUST LOAD FIG. 2

OVEN

' EXHAUST 1o SEASONING MACHINE CIRCUIT THEE-l EXHAUST FIG. 3.

LOAD LAMP ASSEMBLY ON EXHAUST MACHINE 81 START EXHAUSTING OUTER ENVELOPE.

BAKE OUTER ENVELOPE BISEASON INNER ARC TUBE SIMULTANEOUSLY WHILE- OUTER ENVELOPE IS ON EXHAUST.

COOL LAMP ASSEMBLY WHILE ON EXHAUST.

REMOVE EXHAUST a FILL OUTER ENVELOPE WITH NITROGEN TIP OFF OUTER ENVELOPE a UNLOAD FROM EXHAUST MACH.

NITROGEN TO BAKING CIRCUIT INVENTORS.

H D. FRASER 8 N C. UNGLE T.

f/TTUE/VEY.

United States Patent 3,291,548 MERCURY VAPOR LAMP SEASONING AND SEALING METHOD Hugh D. Fraser, West Caldwell, and Melvin C. Unglert,

Wyckolf, N.J., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Jan. 9, 1964, Ser. No. 336,703 6 Claims. (Cl. 316-18) The present invention relates to high pressure mercury vapor lamps and more particularly to a method of seasoning, exhausting and sealing such lamps during their manufacture, which effects a substantial reduction in their manufacturing cost and at the same time improves the quality and increases the lumen output of such lamps.

Heretofore in the manufacture of high pressure mercury vapor lamps, the arc tube has been first assembled in a mount structure which is then sealed into a vitreous outer bulb. The open outer bulb is thereafter baked in a gas oven to a high temperature while it is simultaneously exhausted of evolved deleterious gases, filled with an inert gas, such as nitrogen, and finally sealed-off. After this complete assembly of the lamp the inner arc tube must be operated by the establishment of an arc discharge between its electrodes for a sufiicient period of time to season out deleterious gases usually accumulated therein during its processing. Accordingly, two distinct time consuming operations have been required to complete fabrication of high pressure mercury vapor lamps, which has materially increased their manufacturing cost.

It is accordingly the primary object of the present invention to provide a method of producing a high pressure mercury vapor lamp wherein the baking, seasoning, and exhausting, is all performed in a single operation resulting in a substantial reduction in manufacturing costs.

Another object of the present invention is the provision of a method wherein the seasoning of a high pressure mercury vapor lamp is accomplished by establishment of a discharge in the inner arc tube simultaneously with the baking and exhausting of the outer surrounding envelope whereby evolved gases diffused through the hot inner arc tube along with evolved gases baked out of the interior of the outer surrounding envelope are thoroughly evacuated to thereby enhance the quality of the completed lamp and increase its lumen output.

Another object of the present invention is the provision of a method for baking, seasoning and exhausting, a high pressure mercury vapor lamp in a single operation and wherein the manufacturing cost of fabricating such lamp is still further reduced by utilizing the ballast resistor for the inner arc discharge tube as a source of heat for the baking of such lamp during its fabrication.

The foregoing objects of the present invention, together with other objects which will become obvious to those skilled in the art from the following description are achieved by providing, as a part of the usual exhaust machine, a system which enables the high pressure mercury vapor lamp to be baked, exhausted, seasoned and sealed-off as a single complete operation of such machine. Moreover, heat for the required baking of such lamp is also provided by the ballast resistor which carries the discharge current passing between the electrodes during the seasoning of the arc tube, to still further reduce manufacturing costs of lamp fabrication.

The present invention can be readily understood by reference to the accompanying drawing wherein:

FIGURE 1 is a diagrammatic plan view of an exhaust machine constructed in accordance with the present in-. vention so as to fabricate a high pressure mercury vapor lamp by the method herein disclosed and claimed;

3,291,548 Patented Dec. 13, 1966 FIG. 2 is a sectional view taken on the line IIII of FIG. 1; and

FIG. 3 is a step-chart showing each step of the method of fabricating a high pressure mercury vapor lamp according to the method of the present invention.

Referring now to the drawing as showing one form which the present invention may take, a rotatable table turret 5 of the usual type exhaust machine which indexes through a plurality of stations is shown in FIG. 1. Such turret is provided with numerous heads 6, each of which supports a partially fabricated high pressure mercury vapor lamp 7 by means of its exhaust tubulation 8 forming a vacuum-tight connection therewith, as seen in FIG. 2. Each lamp 7 is loaded into a head 6 as the latter is indexed to the load station as indicated by the legend in FIG. 1. hen the loaded head 6 passes to its next indexed position the interior of the outer lamp envelope is connected by its exhaust tubulation 8 and a conduit 9 to the customary exhaust system and to which it remains connected while indexing through the various stations, as indicated by the outer circular exhaust line in FIG. 1 and which comprises the first step as shown by the step-chart of FIG. 3.

After indexing through several of its numerous exhaust stations each head 6 carrying a loaded lam 7 enters the usual leak detector station for determining leakage in the lamp and between the connection of its exhaust tubulation 8 with the head 6. At its next indexed position the partially fabricated lamp 7 enters a bake oven, indicated by the legend in FIGS. 1 and 2, which oven covers a plurality of stations as shown by the semicircular line bearing the indication Baking and Seasoning of FIG. 1. By reference now more particularly to FIG. 2, it will be noted that the oven is provided with electrical heating elements 12 disposed therein and connected to a baking circuit. A similar type resistor 13 is carried by each head 6 which comprises the ballast for the lamp 7 during operation of its inner arc tube 14 while in the bake oven. In order to connect each inner arc tube 14 to the seasoning circuit, the leading-in conductors 15 and 16 of the lamp 7 are connected to spring contacts 17 forming an integral part of each head 6, with these contacts 17 in turn connected by conductors 18 and brushes 19 to a pair of commutator rings 20 and 22 extending along the inner wall of the bake oven from one end thereof to the other.

Accordingly, as each lamp 7 mounted in its head 6 enters the oven the brushes 19 frictionally engage the respective commutator rings 20 and 22. This completes a circuit from one side of the seasoning circuit through commutator ring 22 and brush 19, one of the conductors 18, a spring clip 17, and leading-in conductor 16 to the inner arc tube 14 and thence back through leading-in conductor 15, remaining spring clip 17 and conductor 18, ballast resistor 13, brush 19 and ring 20 to the other side of the seasoning circuit. An arc discharge is accordingly initiated in the inner arc tube 14 which continues as long as the lamp 7 remains in the oven since the commutator rings, as previously mentioned, extend throughout the latter. Such continued discharge seasons the inner arc tube by driving off occluded gases which diffuse through its heated quartz envelope and are evacuated from the interior of the outer surrounding envelope along with other evolved gases from the baking, by means of the exhaust system. Also, the lamp 7 is simultaneously baked while in the oven by the heat produced by the continuously energized resistance heating elements 12 and the ballast resistor 13 which likewise is continuously energized so long as one or more lamps 7 are within the oven, thus performing the second step as shown by the step-chart of FIG. 3, which simultaneous seasoning and baking improves the quality and increases the lumen output of the finished lamps.

As a specific example for practicing the present method, the outer envelope is baked at a temperature of 450-500" C. for a total period of six minutes. The are tube is seasoned by operating same at its rated power input during the period of baking. In accordance with the practices of the prior art, the lamp baking temperature which was utilized was similar to that which is used in the present method. Because of the positioning of the arc tube and the supports therefor, however, the arc tube and its supports did not reach the baking temperature to which the outer envelope was subjected. As a result, there was some tendency for gaseous impurities to collect on the arc tube and the supports therefor during the lamp baking period. In addition, when the arc tube was later seasoned by operating same, the very high seasoning temperatures tended to drive impurities from the are tube and this impaired lamp performance. By seasoning the arc tube while baking the lamp, in accordance with the present invention, the arc tube and supports therefor are heated to a very high temperature, simultaneous with the baking. As a result, any gaseous impurities which are driven from any interior portion of the partially fabricated lamp are removed by the exhaust. As a further benefit which contributes to lamp improvement, because of the partial vacuum existing between the arc tube and outer envelope during the baking and seasoning operation, the operating temperatures of the arc tube and the supports therefor during the seasoning operation are actually higher than are normally encountered during lamp operation, since the inert gas fill between the arc tube and the outer envelope in a completed lamp removes considerable heat by convection. This higher seasoning temperature for the arc tube and supports therefor serves to drive off all possible impurities, which in turn are removed by the exhaust. As a result, lamps which have been processed during their fabrication in accordance with the present invention display, after 100 hours operation, an improved lumen output averaging about 3.4% as compared to control lamps processed in accordance with the practices of the prior art.

Upon leaving the baking oven each lamp 7 is again indexed to a final leak detector station for a test-check of its vacuum and then the lamps 7 pass through several index stations in a cooling zone, which may comprise a hooded cover, or the like, supplied with a current of cool air, for the purpose of expediting reduction of lamp temperature substantially to atmospheric, and constituting the third step shown by the FIG. 3 step-chart. As the lamp 7 leaves its last indexed exhaust station it is disconnected from the exhaust system by a valve closing, as indicated in FIG. 1, thus holding the vacuum within the outer envelope until it reaches the nitrogen fill" station where it is filled with an inert gas such as nitrogen in accordance with the fourth step shown by FIG. 3. Thereafter the lamp indexes to the tip-off" station at which the outer envelope is sealed by closure 'of the exhaust tubulation 8 in the customary manner, and

unloaded at the next and last station of the exhaust machine 5, shown as the last step in FIG. 3.

It should thus become obvious to those skilled in the are that a method of producing a high pressure mercury vapor lamp has been herein shown and described wherein the exhausting, baking and seasoning is all performed as a single fabricating operation so that when the lamp is unloaded from the machine it is completed ready for basing, packing and shipping. Moreover, by performing all fabricating requirements as a single operation and utilizing the heat generated by the ballast resistor during seasoning of the inner arc tube as a heating element of the baking oven, the manufacturing cost of producing such lamps is very substantially reduced. At the same time the quality of these lamps is materially enhanced because of more complete seasoning and degassing thereof resulting in an increase in lumen output therefrom.

Although one embodiment of the present invention has been shown and described it is to be understood that still further modifications thereof may be made without departing from the spirit and scope of the appended claims.

We claim as our invention:

1. The method of seasoning and sealing a partially fabricated vapor-discharge device comprising a sealed arc-containing envelope mounted within an outer envelope, with electrodes operatively positioned within said arc-containing envelope and connecting to lead-in conductors sealed through said outer envelope, which method comprises:

(a) initiating a discharge between the electrodes of the inner arc-containing envelope to drive off occluded gases,

(b) simultaneously exhausting the outer envelope of evolved gases including any diffused through the hot envelope of the inner arc-containing envelope,

' (c) and thereafter sealing the outer enclosing envelope.

2. The method of seasoning and sealing a partially fabricated high-pressure mercury-vapor discharge device comprising a sealed arc tube mounted within an outer enclosing envelope, with electrodes operatively positioned within said are tube and connecting to lead-in conductors sealed through said outer envelope, which method comprises:

(a) initiating a discharge between the electrodes of the inner arc tube to season the arc tube and driveolf occluded gases,

(b) simultaneously baking the outer enclosing envelope,

(c) exhausting the outer envelope of evolved gases including any diffused through the hot envelope of the inner arc tube,

((1) and thereafter sealing the outer enclosing envelope.

3. The method of seasoning and sealing a partially fabricated high-pressure mercury-vapor discharge device comprising a sealed arc tube mounted within an outer enclosing envelope, with electrodes operatively positioned within said are tube and connecting to lead-in conductors sealed through said outer envelope, which method comprises:

(a) initiating a discharge between the electrodes of the inner arc tube to generate heat and drive-off occluded gases,

(b) simultaneously baking the outer enclosing envelope by applying external heat thereto to supplement the heat generated by the discharge,

(0) exhausting the outer envelope during baking thereof,

(d) and thereafter sealing the outer enclosing envelope.

4. The method of seasoning and sealing a partially fabricated high-pressure mercury-vapor discharge device comprising a sealed arc tube mounted within an outer enclosing envelope, with electrodes operatively positioned within said are tube and connecting to lead-in conductors sealed through said outer envelope, which method comprises:

(a) initiating an externally ballasted discharge between the electrodes of the inner arc tube to season the arc tube and drive-off occluded gases,

(b) simultaneously baking the outer enclosing envelope by applying thereto external heat including that generated by external ballast to supplement the heat generated by the discharge, i

(c) exhausting the outer envelope of evolved gases including any diffused through the hot envelope of the inner arc tube,

(d) and thereafter sealing the outer enclosing envelope.

5. The method of seasoning and sealing a partially fabricated ihigh-pressure mercury-vapor discharge device comprising a sealed arc tube mounted within an outer enclosing envelope, with electrodes operatively positioned within said are tube and connecting to lead-in conductors sealed through said outer envelope, which method comprises:

(a) initiating a discharge between the electrodes of the inner arc tube to generate heat and season such tube,

(b) simultaneously baking the outer enclosing envelope by applying external heat thereto to supplement the heat generated by the discharge,

(c) exhausting the outer envelope during such seasoning and baking of evolved gases including any difiused through the hot envelope of the inner arc tube,

(d) cooling the partially fabricated device and filling the outer enclosing envelope with an inert gas,

(e) and sea-ling the outer enclosing envelope.

6. The method of seasoning and sealing a partially fabricating high-pressure mercurcy-vapor discharge device comprising a sealed arc tube mounted within an outer enclosing envelope, with electrodes operatively positioned within said are tube and connecting to lead-in conductors 6 sealed through said outer envelope, which method comprises:

(a) initiating an externally ballasted discharge between the electrodes of the inner arc tube to generate heat and season the arc tube,

(b) simultaneously baking the outer enclosing envelope by applying thereto external heat including that generated by external ballast to supplement that heat generated by the discharge,

(0) exhausting the outer envelope during such seasoning and baking of evolved gases including any diifused through the hot envelope of the inner arc tube,

(d) filling the outer envelope with an inert gas,

(e) and sealing the outer enclosing envelope.

References Cited by the Examiner UNITED STATES PATENTS 1,677,900 7/1924 McCullough 31618 RICHARD H. EANES, 111., Primary Examiner. 

1. THE METHOD OF SEASONING AND SEALING A PARTIALLY FABRICATED VAPOR-DISCHARGE DEVICE COMPRISING A SEALED ARC-CONTAINING ENVELOPE MOUNTED WITHIN AN OUTER ENVELOPE, WITH ELECTRODES OPERATIVELY POSITIONED WITHIN SAID ARC-CONTAINING ENVELOPE AND CONNECTING TO LEAD-IN CONDUCTORS SEALED THROUGH SAID OUTER ENVELOPE, WHICH METHOD COMPRISES: (A) INITIATING A DISCHARGE BETWEEN THE ELECTRODES OF 